BOPAM’s Bright and Dark Excited States: Insight from Structural, Photophysical, and Quantum Chemical Investigations
BOPAM exhibits high fluorescence quantum yields, along with exceptional photostability, rendering it a promising platform for applications as fluorescence sensors. However, the development of BOPAM-based fluorophores with extended emission wavelengths remains limited, and the underlying mechanisms o...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/13/2673 |
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| Summary: | BOPAM exhibits high fluorescence quantum yields, along with exceptional photostability, rendering it a promising platform for applications as fluorescence sensors. However, the development of BOPAM-based fluorophores with extended emission wavelengths remains limited, and the underlying mechanisms of fluorescence quenching via the population of dark twisted intramolecular charge transfer (<sup>1</sup>TICT) excited states are not yet fully understood. To address these gaps, we synthesized a series of BOPAM derivatives by incorporating electron-donating groups at the boron atoms and the phenyl rings of the BOPAM core. The introduction of bromide, phenyl, and naphthyl groups preserved the intrinsic locally excited (<sup>1</sup>LE) emission of BOPAM. In contrast, the incorporation of diphenylamine (<b>BP-DA</b>) and triphenylamine (<b>BP-TA</b>) moieties resulted in a red-shifted emission, attributed to an enhanced intramolecular charge transfer (ICT) process. Notably, in acetonitrile, <b>BP-DA</b> exhibited weak fluorescence originating from a <sup>1</sup>TICT state, which was populated via the S<sub>2</sub> → <sup>1</sup>TICT transition. Furthermore, the emission observed from <b>BP-TA</b> was associated with a higher-lying excited state, likely the initially populated S<sub>2</sub> state possessing a <sup>1</sup>LE character. These findings not only introduce novel red-emissive BOPAM-based fluorophores, but also offer valuable insights into the role of the S<sub>2</sub> state in governing fluorescence quenching mechanisms in BOPAM derivatives. |
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| ISSN: | 1420-3049 |